This project will be a continuation of previous research on the changes in chemical nature and metabolism of basic chromosomal proteins which occur at various stages of spermatogenesis in testes of the rat. A study will be made of the role of gonadotropic hormones and testosterone in the regulation of the synthesis, phosphorylation, and acetylation of the unusual histone subfractions, TH1-x and TH2b-x, which occur in seminiferous epithelial cells of the testis and may be involved in meiosis. The role of nuclear proteases in these changes in chromosomal proteins will be studied.